800g Tank Reseal (for the 2nd time)!

[jjohnwm]

Wow, this thing just does not want to hold water. I am starting to wonder if the previous owner chased this leak around for a few months or years before throwing in the towel and selling it.

It's more than twice the size of anything I've ever built...it's about 8x the size of the biggest glass tank I've ever built...so I'm afraid to make any suggestions. But it's not my house, so...I will!

I wonder: is there a chance that during the original construction of this tank, the bottom glass (which, as others have commented, is pretty dang thin...) might have been laying on a surface which was not completely flat? A very slight twist, cause by warped wood surfaces and/or perhaps some small obstruction lahying un-noticed under the glass, might perhaps have allowed the big-yet-thin sheet of glass to flex almost imperceptibly. Then, the four sides were assembled on top of it, the silicone cured, and the tank then moved into position. The stand, being perfectly flat and level, would not be supporting the bottom completely or evenly. I'm not talking about giant gaps here, perhaps enough to slip a coupe sheets of paper between the bottom and the stand in one corner or two.

You then fill it with water, the weight of which is pressing down on the entire bottom, which flexes slightly as the higher corners press down to the stand. This then stresses the structural bead between the sides and the bottom; it was okay for a few years but as the silicone ages the constant flexing begins to tear it, resulting in your leak.

How about the four vertical corner seams? Is each of them perfectly smooth, or does one of the sides sit slightly proud of the adjoining side at any point? That might be an indicator of a tank that isn't built completely square and true, but is trying to be under the weight of water.

Just thinking out loud here; I've got nothing better.

 

[Backfromthedead]

Wow, this thing just does not want to hold water. I am starting to wonder if the previous owner chased this leak around for a few months or years before throwing in the towel and selling it.

It's more than twice the size of anything I've ever built...it's about 8x the size of the biggest glass tank I've ever built...so I'm afraid to make any suggestions. But it's not my house, so...I will!

I wonder: is there a chance that during the original construction of this tank, the bottom glass (which, as others have commented, is pretty dang thin...) might have been laying on a surface which was not completely flat? A very slight twist, cause by warped wood surfaces and/or perhaps some small obstruction lahying un-noticed under the glass, might perhaps have allowed the big-yet-thin sheet of glass to flex almost imperceptibly. Then, the four sides were assembled on top of it, the silicone cured, and the tank then moved into position. The stand, being perfectly flat and level, would not be supporting the bottom completely or evenly. I'm not talking about giant gaps here, perhaps enough to slip a coupe sheets of paper between the bottom and the stand in one corner or two.

You then fill it with water, the weight of which is pressing down on the entire bottom, which flexes slightly as the higher corners press down to the stand. This then stresses the structural bead between the sides and the bottom; it was okay for a few years but as the silicone ages the constant flexing begins to tear it, resulting in your leak.

How about the four vertical corner seams? Is each of them perfectly smooth, or does one of the sides sit slightly proud of the adjoining side at any point? That might be an indicator of a tank that isn't built completely square and true, but is trying to be under the weight of water.

Just thinking out loud here; I've got nothing better.

I had a 150 that was just like that. Sat on two corners when it was empty than laid flat when full. Always gave me the willies. It's a solid theory.

 

[Trouser Cough]

I wonder: is there a chance that during the original construction of this tank, the bottom glass (which, as others have commented, is pretty dang thin...) might have been laying on a surface which was not completely flat? A very slight twist, cause by warped wood surfaces and/or perhaps some small obstruction lahying un-noticed under the glass, might perhaps have allowed the big-yet-thin sheet of glass to flex almost imperceptibly. Then, the four sides were assembled on top of it, the silicone cured, and the tank then moved into position. The stand, being perfectly flat and level, would not be supporting the bottom completely or evenly. I'm not talking about giant gaps here, perhaps enough to slip a coupe sheets of paper between the bottom and the stand in one corner or two.

When I bought the tank (2nd hand) it appeared to be brand new. Apparently a few years old but still had the paper stickers on the glass and the inside appeared to be pristine. It was a couple hundred miles away and bumped its way to my house in the back of my F350. Once it got here it remained in the back of that truck for a good while as I had to figure out a way to get it out.

That seal held for a while and then gave out.

I resealed the tank myself and it held for a couple three years then failed. That was due to an apparently very thin section of sealant that eventually gave way.

I have yet to check P&A on glass strips but that sounds like a fairly easy fix.

The more I think about this the moreI like the idea of a simpe glass strip install at the inside bottom perimeter. I've seen other tanks w/ similar strips inside and never knew what they were for. In the end this is just sticky goop bonding one piece of glass to the next and if given the chance I'll introduce complexity where it doesn't belong.

SCS1200, glass strips and done.

I have a vague recollection of climbing into that tank w/ a leg w/ fresh screws in it and balancing my weight at the mid-point of the front pane and then wobbling around on one foot once inside to keep from falling.

That was probably pretty tough on what we're calling the structural seam and had I known then what I know now...

I also think that once the tank is cleaned I'll install the longer strips from outside the tank such that my weight isn't moving the sealant. I'll see if I can find a long nozzle for the caulking tubes and splooge that stuff in from outside and above the tank.

We'll know more in a month or so.

In the interim I've got a couple longer term tanks to set up.

 

[jjohnwm]

I had a 150 that was just like that. Sat on two corners when it was empty than laid flat when full. Always gave me the willies. It's a solid theory.

I'm relieved to hear some agreement on that; I read and re-read my suggestion a couple times before hitting Send. Wasn't sure if it was a legitimate concern, as I have never dealt with a tank displaying that problem...but it seemed theoretically possible.

Trouser Cough , keep in mind that the structural bead between glass panes is The Tank. It's what holds the thing together. The internal bead is just an added insurance policy, and in the vast majority of tanks it is strictly cosmetic. I guess it affords a bit of protection to the structural bead from inexpertly wielded razor blades during algae removal, and if perchance the structural bead is imperfect it will indeed prevent a leak, but...by and large it isn't necessary. A carefully and properly constructed tank will almost always be waterproof without the addition of an internal bead, but unless you have God-like construction skills like my old boss Ivan, there will always be some extra silicone squeezed out into the interior when the glass is assembled. Finger-smoothing that into a nice concave bead is a hell of a lot faster and easier than removing it, so that's what is done. That internal bead contributes virtually nothing to the strength of the tank...but it makes it more saleable and profitable because it is what people have come to expect, and it's much easier to do a tank with it rather than without it.

I think the idea of internal braces along the bottom front and rear is the way to go, and if you can do them working from outside the tank, all the better. A generous squiggle of silicone, drop the brace on it, squeeze it into place, and then complete the entire inner bead including around the brace all in one fell swoop.

Whatever you do, be careful about it. If it still leaks after this...you will have a much bigger PITA to remove this and re-try it. Good luck!

 

[Trouser Cough]

No God-like construction skills here though I am hoping for a little divine intervention and hope is always such an xlnt strategy.

I'll have a ton more SCS1200 in black ordered this weekend and I'll get P&A on the glass strips on Monday.

I very much appreciate the input from you all and it sounds like you've identified the snafu. This is about to get interesting for sure.

As long as we're on the topic of wishing and hoping I should be clear on two things...

- I wish I had never botched that structural bead, and

- I had no idea this might be so tough.

 

[jjohnwm]

I just re-read the thread....and I gotta say that it is worrying me more and more.

There is no way in hell that the new bead, even if it is being pulled loose by the removal of tape, should be able to pull the old structural silicone out from between the panes. There is no adhesion between the old and the new stuff; how can it be pulling it out? Or was I misinterpreting your explanation?

Silicone adhesion to glass is pretty strong with proper preparation before assembly. I just don't understand how that structural bead could possibly be pulled loose by anything external...unless that structural seam has been seriously...seriously...compromised in some way, either by improper preparation of the glass way back during initial construction, or something else.

I also just noticed that the leaks are separate and discreet from one another. That creeped me right out because to me it implies that the whole thing is on the verge of letting go.

If there is something that has interfered with proper adhesion of that structural bead, I don't believe for a second there is any way to clean it out and replace it, short of complete disassembly and reconstruction of the whole tank. Who knows? Might the tank have originally been constructed using old past-expiry-date silicone? Is this the way that would manifest itself? How does expired silicone fail?

Sorry, I don't want to be negative, but...all things considered...I have totally lost confidence in the viability of this repair project. If it were me...the only way I would proceed would be a complete teardown, insanely painstaking cleaning, and rebuild into essentially a new tank, complete with nice thick internal braces running the full length of the bottom seam on all four sides. Or...since I've never built a glass tank anything like this...I'd just buy a new tank.

 

[M1A1]

I think what TC mentioned was that he may have cut into the structural seam when cleaning up the internal sealant so the seam hasn't had silicone removed but it's been cut into randomly and those small sections have reduced strength, or maybe are cut clear through. That's my guess for the separate distinct leaks. If the seam was truly compromised then hell would have let loose and those morning nudges to check the basement would have been more vigorous. The ones I receive certainly are.

Buuuuuut yeah the only way to truly fix that would be total disassembly. Maybe you find someone that says it can be done with the injection method but that's a yikes to me. Internal or external bracing is going to be a patch no matter what. I do think the tank should have come from the manufacturer with an internal eurobrace considering the dimensions and glass thickness used. That would add a ton of strength and a secondary structural seam.

I'm not sure about the silicone not sticking or not curing as it does look like some of it adhered well enough. Distributors and retailers love to clean out those stagnant inventory items so it's on you to be checking expiration dates and batch codes to see if it's still good.